1. Field of the Invention
The present invention relates to a fuel tank for an engine mounted on a working machine of a self-propelled type such as a lawn mower, and particularly to a fuel tank system which is designed so that impure foreign substances such as water and dust incorporated in a fuel cannot be supplied to a fuel supply means in an engine, even when a fuel tank is repeatedly tilted.
2. Description of the Related Art
There is a generally known fuel tank system for an agricultural working machine of a self-propelled type, in which a fuel flow-in bore 6 communicating with a fuel tank 1 is opened, at a proper height from the bottom plate 3, into a sidewall of a discharge pipe 4 secured to a lowermost bottom plate 3 of a bottom wall of the fuel tank 1, so that dust accumulated in the bottom of the fuel tank 1 cannot be sucked into the discharge pipe 4 (see Japanese Utility Model Publication No. 56-55050).
In the fuel tank system disclosed in the above-described patent document, however, even if the fuel flow-in bore 6 of the discharge pipe 4 situates at a position higher than the bottom plate 3, it is difficult to reliably avoid that the dust accumulated on the bottom of the fuel tank 1 is sucked into the discharge pipe 4 through the fuel flow-in bore 6.
In order to eliminate the above-described drawback, a fuel tank system has been already proposed, in which a downward-depressed collecting recess for collecting dust and the like is formed in a portion of a bottom plate of a fuel tank; a strainer chamber with a suction bore opened into its upper surface is provided in the collecting recess; a fuel discharge pipe is connected to a bottom of the strainer chamber; and a fuel free of dust, after being filtered, is guided from the strainer chamber through the fuel discharge pipe to a fuel supply means for an engine, as shown in FIGS. 8 and 9.
In the proposed fuel tank system, however, there is the following problem: the strainer chamber is disposed in a narrower space in the collecting recess in the bottom of the fuel tank, and there is little space for flowing of the fuel outside the strainer chamber; thus, every time the fuel tank is tilted, the fuel containing impure foreign substances such as water and dust may collide with an end wall of the strainer chamber to splash up and pass over an upper surface of the strainer chamber; during this time, the impure foreign substances are passed through the suction bore and sucked into the strainer chamber, and then caused to flow along with the fuel to an fuel supply means such as a carburetor, thereby causing an operational failure of the fuel supply means.